Abstract: By studying free form surface inspection, an algorithm of the graphics based best fit in relation to two surfaces is presented for solving coordinate deviation in inspection procedures. Using the affine invariance of parametric surface, a better original position for surface fitting calculation is applied firstly. After that,the optimal algorithm can be efficiently carried out by randomly or interactively choosing some measure points.The application shows that the algorithm presented in this paper can minimize coordinate deviation efficiently,and has good robustness.The algorithm has been successfully used in reverse engineering software RE-SOFT.

Key words: sur face inspection, best fit, optimization